Sealing sheet

Abstract

The present invention is a sealing sheet having a curable sealant layer, characterized in that the following requirements (I), (II) and (III) are satisfied. Requirement (I): The sealant layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher. Requirement (II): The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group. Requirement (III): The relative dielectric constant of the cured product of the sealant layer is less than 3.5 at 23°C and a frequency of 100 kHz. According to the present invention, a sealing sheet having a sealant layer can be provided, wherein the sealant layer forms a cured product having low dielectric properties and excellent transparency.

Description

Technical Field

[0001] The present invention relates to a sealing sheet having a curable sealing agent layer. Background Art

[0002] In recent years, organic EL elements have attracted attention as light-emitting elements capable of emitting light with high brightness by low-voltage direct-current driving.

[0003] However, organic EL elements have a problem in that light emission characteristics such as light emission brightness, light emission efficiency, and light emission uniformity are prone to deterioration over time.

[0004] As a cause of the problem of reduced light emission characteristics, oxygen, water, etc. may penetrate into the interior of the organic EL element and deteriorate the electrodes or the organic layer. Therefore, the organic EL element is sealed with a sealing material to prevent the penetration of oxygen or water.

[0005] For example, Patent Document 1 describes an image display device sealing material, which is characterized in that it contains a resin component and a curing agent, wherein the resin component contains an epoxy resin containing a biphenyl skeleton with a weight average molecular weight within a specific range, an epoxy resin containing an alicyclic skeleton with a weight average molecular weight within a specific range, and a styrene-based oligomer with a weight average molecular weight within a specific range.

[0006] Patent document 1 also states that since the image display device sealing material contains a resin containing a biphenyl skeleton and a styrene-based oligomer, its dielectric constant is low, and by using the image display device sealing material as a sealing material in a touch panel, it is less likely to cause a touch panel failure caused by the sealing material.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent document 1: WO2018 / 235824. Summary of the invention

[0010] Problems to be solved by the invention

[0011] As described in Patent Document 1, a curable sheet-like adhesive is suitably used as a material for forming a sealing material (hereinafter, "a sheet-like adhesive for forming a sealing material" may be referred to as a "sealant layer").

[0012] In particular, a sealant layer that provides a cured product having low dielectric properties is useful as a material for forming a sealant material for a touch panel or the like.

[0013] An object of the present invention is to provide a sealing sheet more suitable as a material for forming a sealing material used for a touch panel or the like (ie, a sealing sheet having a sealing agent layer that forms a cured product having low dielectric properties and excellent transparency).

[0014] Means of solving problems

[0015] The present inventors have conducted in-depth research on curable sealant layers in order to solve the above problems. As a result, they found that a cured adhesive layer containing a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher and a compound having an alicyclic skeleton and a cyclic ether group has low dielectric properties and excellent transparency, thereby completing the present invention.

[0016] Therefore, according to the present invention, the following sealing sheets [1] to [7] can be provided.

[0017] [1] A sealing sheet having a curable sealant layer, characterized in that the following requirements (I), (II) and (III) are satisfied:

[0018] Requirement (I): The sealant layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher;

[0019] Requirement (II): The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group;

[0020] Requirement (III): The relative dielectric constant of the cured product of the sealant layer at 23° C. and a frequency of 100 kHz is 3.5 or less.

[0021] [2] The sealing sheet according to [1], wherein the cured product of the sealant layer has a dielectric loss tangent of 0.05 or less at 23° C. and a frequency of 100 kHz.

[0022] [3] The sealing sheet according to [1] or [2], wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound that is liquid at 25°C.

[0023] [4] The sealing sheet according to any one of [1] to [3], wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound having a glycidyl ether group as the cyclic ether group.

[0024] [5] The sealing sheet according to any one of [1] to [4], wherein the cured product of the sealant layer has a total light transmittance of 90% or more.

[0025] [6] The sealing sheet according to any one of [1] to [5], wherein a cured product of the sealant layer has a haze value of 1% or less.

[0026] [7] The sealing sheet according to any one of [1] to [6], wherein the cured product of the sealant layer has a b* value of -1 to +1 in the CIE 1976 L*a*b* color space.

[0027] Effects of the Invention

[0028] According to the present invention, there is provided a sealing sheet having a sealing compound layer which forms a cured product having low dielectric properties and excellent transparency. DETAILED DESCRIPTION

[0029] The sealing sheet of the present invention is a sealing sheet having a curable sealant layer, and is characterized by satisfying the following requirements (I), (II) and (III).

[0030] Requirement (I): The sealant layer contains a phenoxy resin having a glass transition temperature (Tg) of 90° C. or higher.

[0031] Requirement (II): The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group.

[0032] Requirement (III): The relative dielectric constant of the cured product of the sealant layer at 23° C. and a frequency of 100 kHz is 3.5 or less.

[0033] In the present invention, the "sealant layer" means a "sheet-shaped adhesive for forming a sealant." The cured product of the sealant layer is used as a sealant.

[0034] The sealant layer is a layer that exhibits non-fluidity at room temperature. The sealant layer may be in a short strip shape or a long strip shape (ribbon shape).

[0035] [Requirement (I)]

[0036] The sealant layer contains a phenoxy resin (hereinafter, sometimes referred to as “phenoxy resin (A)”) having a glass transition temperature (Tg) of 90° C. or higher.

[0037] Phenoxy resin is a polymer with a main chain of an addition polymerization structure of an aromatic diol and an aromatic diglycidyl ether. Phenoxy resin is generally equivalent to a high molecular weight epoxy resin and refers to a resin with a polymerization degree of about 100 or more.

[0038] The phenoxy resin (A) is important in that the characteristics of the compound having an alicyclic skeleton and a cyclic ether group (hereinafter, sometimes described as "cyclic ether group-containing compound (B)") are fully utilized.

[0039] That is, as described below, in order to reduce the dielectric constant of the cured product of the sealant layer and further improve the transparency of the cured product of the sealant layer, it is preferred that the sealant layer contain a large amount of the cyclic ether group-containing compound (B).

[0040] However, a sealant layer containing a large amount of the cyclic ether group-containing compound (B) may have reduced shape retainability before curing.

[0041] In this regard, since the sealant layer of the sealing sheet of the present invention contains the phenoxy resin (A), even when a large amount of the cyclic ether group-containing compound (B) is contained, the shape before curing can be maintained at a constant shape for a long period of time.

[0042] The glass transition temperature (Tg) of the phenoxy resin (A) is 90°C or higher, preferably 95 to 150°C, and more preferably 100 to 150°C.

[0043] When the glass transition temperature (Tg) of the phenoxy resin (A) is 90° C. or higher, the cured product of the sealant layer has excellent shape retainability under high temperature conditions.

[0044] The glass transition temperature (Tg) of the phenoxy resin (A) can be measured using a differential scanning calorimeter.

[0045] The weight average molecular weight (Mw) of the phenoxy resin (A) is usually 10,000 to 200,000, preferably 20,000 to 100,000, and more preferably 30,000 to 80,000.

[0046] If the weight average molecular weight (Mw) of the phenoxy resin (A) is too small, the sealant layer tends to have difficulty in maintaining a constant shape, while if the weight average molecular weight (Mw) of the phenoxy resin (A) is too large, the sealant layer tends to have poor handleability.

[0047] The weight average molecular weight (Mw) of the phenoxy resin (A) can be determined as a standard polystyrene-equivalent value by performing gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0048] The epoxy equivalent of the phenoxy resin (A) is preferably 5,000 g / eq or more, more preferably 6,500 g / eq or more. The epoxy equivalent can be measured in accordance with JIS K7236.

[0049] Examples of the phenoxy resin (A) include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol S type phenoxy resin, bisphenol A type and bisphenol F type copolymer type phenoxy resin, bisphenol E type phenoxy resin, naphthalene type phenoxy resin, phenolic resin type phenoxy resin, biphenyl type phenoxy resin, and cyclopentadiene type phenoxy resin.

[0050] The phenoxy resin (A) can be used alone or in combination of two or more.

[0051] The phenoxy resin (A) can be obtained by a method of reacting a bifunctional phenol with an epihalohydrin to obtain a high molecular weight, or by a method of subjecting a bifunctional epoxy resin to a polyaddition reaction with a bifunctional phenol.

[0052] For example, it can be obtained by reacting a difunctional phenol with an epihalohydrin in the presence of an alkali metal hydroxide in an inert solvent at a temperature of 40 to 120° C. Alternatively, it can be obtained by heating a difunctional epoxy resin with a difunctional phenol in the presence of a catalyst such as an alkali metal compound, an organic phosphorus compound, a cyclic amine compound, in an organic solvent such as an amide solvent, an ether solvent, a ketone solvent, a lactone solvent, an alcohol solvent, etc., with a boiling point of 120° C. or more to 50 to 200° C. at a reaction solid content concentration of 50% by weight or less to perform a polyaddition reaction.

[0053] The difunctional phenols are not particularly limited as long as they are compounds having two phenolic hydroxyl groups. For example, monocyclic difunctional phenols such as hydroquinone, 2-bromohydroquinone, resorcinol, and catechol, bisphenols such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S, dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl, and dihydroxyphenyl ethers such as bis(4-hydroxyphenyl)ether, and compounds obtained by introducing a straight-chain alkyl group, a branched-chain alkyl group, an aryl group, a hydroxymethyl group, an allyl group, a cyclic aliphatic group, a halogen (tetrabromobisphenol A, etc.), a nitro group, etc., into the aromatic ring of these phenol skeletons, and polycyclic difunctional phenols obtained by introducing a straight-chain alkyl group, a branched-chain alkyl group, an allyl group, an allyl group with a substituent, a cyclic aliphatic group, an alkoxycarbonyl group, etc., into the carbon atom located in the center of these bisphenol skeletons.

[0054] Examples of the epihalohydrin include epichlorohydrin, epibromohydrin, and epiiodohydrin.

[0055] In the present invention, a commercially available phenoxy resin (A) may be used, and examples of the commercially available phenoxy resin include YX7200 (glass transition temperature: 150°C), YX6954 (phenoxy resin containing a bisphenol acetophenone skeleton, glass transition temperature: 130°C), and jER1256 (glass transition temperature: 98°C) (all manufactured by Mitsubishi Chemical Corporation).

[0056] The content of the phenoxy resin (A) is preferably 30 to 55% by mass, more preferably 35 to 50% by mass, based on the entire sealant layer.

[0057] When the content of the phenoxy resin (A) is within the above range, the shape retainability of the sealant layer is improved, and a sealant layer that forms a cured product having low dielectric properties and excellent transparency is easily obtained.

[0058] In the present invention, "having low dielectric properties" means satisfying requirement (III).

[0059] [Requirement (II)]

[0060] The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group [cyclic ether group-containing compound (B)].

[0061] The compound having an alicyclic skeleton and a cyclic ether group refers to a compound having an alicyclic skeleton and at least one, preferably two or more, cyclic ether groups in the molecule. It should be noted that in the present invention, phenoxy resin (A) is not included in the compound having an alicyclic skeleton and a cyclic ether group.

[0062] When the sealant layer contains the cyclic ether group-containing compound (B), the cured product of the sealant layer has low dielectric properties and excellent transparency.

[0063] The molecular weight of the cyclic ether group-containing compound (B) is usually 100 to 5,000, preferably 200 to 3,000.

[0064] The cyclic ether equivalent of the cyclic ether group-containing compound (B) is preferably 50 g / eq or more and 1000 g / eq or less, and more preferably 100 g / eq or more and 800 g / eq or less.

[0065] By curing the sealant layer in which the cyclic ether equivalent of the cyclic ether group-containing compound (B) is within the above range, a sealing material having high adhesive strength can be formed more efficiently.

[0066] The cyclic ether equivalent in the present invention refers to a value obtained by dividing the molecular weight by the number of cyclic ether groups.

[0067] Examples of the cyclic ether group include an oxirane group (epoxy group), an oxetane group (oxetanyl group), a tetrahydrofuranyl group, and a tetrahydropyranyl group.

[0068] Among them, the cyclic ether group is preferably an ethylene oxide group.

[0069] In addition, in this specification, an oxirane group includes the group which has an oxirane structure, such as a glycidyl group, a glycidyl ether group, and an epoxycyclohexyl group.

[0070] Examples of the cyclic ether group-containing compound (B) include cycloolefin oxide compounds such as polyglycidyl ethers of polyols having at least one alicyclic structure, and compounds containing cyclohexene oxide or cyclopentene oxide obtained by epoxidizing a cyclohexene or cyclopentene ring-containing compound with an oxidizing agent.

[0071] Representative examples of the cyclic ether group-containing compound (B) include hydrogenated bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methylhexylcarboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexylcarboxylate, 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexylcarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexylcarboxylate, bis(3,4-epoxycyclohexylmethyl)-3,4-epoxy-5-methylcyclohexylcarboxylate, 4-epoxycyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), propane-2,2-diyl-bis(3,4-epoxycyclohexane), 2,2-bis(3,4-epoxycyclohexyl)propane, dicyclopentadiene diepoxide, ethylenebis(3,4-epoxycyclohexanecarboxylate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1-epoxyethyl-3,4-epoxycyclohexane, 1,2-epoxy-2-epoxyethylcyclohexane, α-pinene oxide, limonene dioxide, etc.

[0072] In addition, as the compound (B) containing a cyclic ether group, commercially available products can also be used. Commercially available products include Celloxide 2021P, Celloxide 2081, Celloxide 2000, Celloxide 3000 (all manufactured by Daicel Corporation), Epolight 4000 (manufactured by Kyoeisha Chemical Co., Ltd.), YX8000, YX8034 (manufactured by Mitsubishi Chemical Corporation), ADEKA RESIN EP-4088S, ADEKA RESIN EP-4088L, ADEKA RESIN EP-4080E (manufactured by ADEKA Corporation), etc.

[0073] The cyclic ether group-containing compound (B) can be used alone or in combination of two or more.

[0074] The content of the cyclic ether group-containing compound (B) is preferably 45% by mass or more, more preferably 55 to 70% by mass, based on the entire sealant layer.

[0075] When the content of the cyclic ether group-containing compound (B) is 50% by mass or more based on the entire sealant layer, a cured product of the sealant layer having a lower dielectric constant and more excellent transparency can be easily obtained.

[0076] At least one of the cyclic ether group-containing compounds (B) is preferably a liquid compound at 25°C.

[0077] “Liquid at 25° C.” means having fluidity at 25° C. The cyclic ether group-containing compound (B) preferably has a viscosity of 2 to 10,000 mPa·s as measured at 25° C. and 1.0 rpm using an E-type viscometer.

[0078] By using a cyclic ether group-containing compound (B) that is liquid at 25° C., it is easy to form a sealant layer having more excellent adhesiveness at room temperature (25° C., the same applies hereinafter).

[0079] When the sealant layer contains the cyclic ether group-containing compound (B) which is liquid at 25°C, the content thereof is preferably 55% by mass or more, more preferably 55 to 70% by mass, based on the entire sealant layer.

[0080] When the content of the epoxy compound that is liquid at 25° C. is 55% by mass or more based on the entire sealant layer, it is easy to form a sealant layer having more excellent adhesiveness at room temperature.

[0081] At least one of the cyclic ether group-containing compounds (B) is preferably a compound having a glycidyl ether group as the cyclic ether group.

[0082] Since the reactivity of a glycidyl ether group is not so high compared with an epoxycyclohexyl group, by using the cyclic ether group-containing compound (B) having a glycidyl ether group, a sealing sheet having more excellent storage stability can be easily obtained.

[0083] When the sealant layer contains the cyclic ether group-containing compound (B) having a glycidyl ether group, the content thereof is preferably 55% by mass or more, more preferably 55 to 70% by mass, based on the entire sealant layer.

[0084] When the content of the cyclic ether group-containing compound (B) having a glycidyl ether group is 55% by mass or more based on the entire sealant layer, a sealing sheet having more excellent storage stability can be easily obtained.

[0085] [Requirement (III)]

[0086] The relative dielectric constant of the cured product of the sealant layer at 23° C. and a frequency of 100 kHz (hereinafter, this relative dielectric constant may be referred to as “relative dielectric constant (α)”) is 3.5 or less.

[0087] By using a cured product having a relative dielectric constant (α) of 3.5 or less as a sealing material in an electronic device including a touch sensor such as a touch panel, it is possible to suppress malfunction of the electronic device caused by the sealing material.

[0088] The relative dielectric constant (α) is preferably 3.48 or less, more preferably 3.47 or less.

[0089] The lower limit of the relative dielectric constant (α) is not particularly limited, but is usually 2.00 or more.

[0090] The sample for measuring the relative dielectric constant (α) is not particularly limited as long as the sealant layer is sufficiently cured.

[0091] For example, when the sealant layer has thermosetting properties, a cured product obtained under curing conditions of 110° C. for 1 hour can be used as a measurement sample for the relative dielectric constant (α).

[0092] The relative dielectric constant (α) can be measured according to the method described in the Examples.

[0093] The cured product of the sealant layer containing a large amount of the cyclic ether group-containing compound (B) tends to have a small relative dielectric constant (α).

[0094] Therefore, the sealant layer satisfying the requirement (III) can be efficiently formed by adjusting the content of the cyclic ether group-containing compound (B).

[0095] [Curing agent]

[0096] The sealant layer may contain a curing agent. By using a curing agent, a sealant layer in which a curing reaction proceeds more efficiently can be obtained.

[0097] The curing agent is not particularly limited as long as it is a curing agent that initiates a curing reaction of at least the cyclic ether group-containing compound (B). Since the curing reaction can be completed in a relatively short time, a curing agent that initiates a curing reaction by heating is preferably used as the curing agent.

[0098] Examples of the curing agent that initiates a curing reaction by heating include a thermal cationic polymerization initiator and other heat-reactive curing agents.

[0099] The thermal cationic polymerization initiator is a compound that can generate cationic species that initiate polymerization by heating.

[0100] Examples of the thermal cationic polymerization initiator include sulfonium salts, quaternary ammonium salts, Salt, diazonium salt, iodine Salt, etc.

[0101] Examples of the sulfonium salt include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroarsenate, tri(4-methoxyphenyl)sulfonium hexafluoroarsenate, and diphenyl(4-phenylthiophenyl)sulfonium hexafluoroarsenate.

[0102] As the sulfonium salt, a commercially available product may be used. Commercially available products include Adeka Opton SP-150, Adeka Opton SP-170, Adeka Opton CP-66, Adeka Opton CP-77 (all manufactured by Asahi Denka Corporation), SAN-AIDSI-60L, SAN-AID SI-80L, SAN-AID SI-100L, SAN-AID SI-B2A, SAN-AID SI-B3 (all manufactured by Sanshin Chemical Co., Ltd.), CYRACURE UVI-6974, CYRACURE UVI-6990 (all manufactured by Union Carbide Corporation), UVI-508, UVI-509 (all manufactured by General Electric Company), FC-508, FC-509 (all manufactured by Minnesota Mining and Manufacturing Company), CD-1010, CD-1011 (all manufactured by Sartomer Corporation), CI series products (manufactured by Nippon Soda Co., Ltd.), etc.

[0103] Examples of the quaternary ammonium salt include tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, tetraethylammonium p-toluenesulfonate, N,N-dimethyl-N-benzylaniline hexafluoroantimonate, N,N-dimethyl-N-benzylaniline tetrafluoroborate, N,N-dimethyl-N-benzylpyridine Hexafluoroantimonate, N,N-diethyl-N-benzyl trifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridine Hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl)toluidine hexafluoroantimonate, etc.

[0104] As Salts include ethyltriphenylphosphine Hexafluoroantimonate, tetrabutyl Hexafluoroantimonate, etc.

[0105] Examples of the diazonium salt include AMERICURE (manufactured by American Can Company) and ULTRASET (manufactured by Asahi Denka Corporation).

[0106] As iodine Salts, such as diphenyl iodide Hexafluoroarsenate, bis(4-chlorophenyl)iodide Hexafluoroarsenate, bis(4-bromophenyl)iodide Hexafluoroarsenate, phenyl (4-methoxyphenyl) iodide Hexafluoroarsenate, etc. In addition, as commercially available products, UV-9310C (manufactured by Toshiba Silicone Co., Ltd.), Photoinitiator 2074 (manufactured by Rhoneporenc), UVE series products (manufactured by General Electric Company), FC series products (manufactured by Minnesota Mining and Manufacturing Company), etc. can also be used.

[0107] Examples of heat-reactive curing agents other than the thermal cationic polymerization initiator include amine compounds such as benzylmethylamine and 2,4,6-tris(dimethylaminomethyl)phenol; imidazole compounds such as 2-methylimidazole, 3-ethyl-4-methylimidazole and 2-heptadecylimidazole; and Lewis acids such as boron trifluoride-monoethylamine complex and boron trifluoride-piperazine complex.

[0108] The curing agent may be used alone or in combination of two or more.

[0109] The content of the curing agent is not particularly limited, but is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, based on 100 parts by mass of the cyclic ether group-containing compound (B).

[0110] [Silane coupling agent]

[0111] The sealant layer may contain a silane coupling agent. By using a silane coupling agent, a sealant layer having better wet heat durability can be easily obtained.

[0112] As the silane coupling agent, a known silane coupling agent can be used, among which an organic silicon compound having at least one alkoxysilyl group in the molecule is preferred.

[0113] Examples of the silane coupling agent include silane coupling agents having a (meth)acryloyl group such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

[0114] Silane coupling agents having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, trichlorovinylsilane, and vinyltri(2-methoxyethoxy)silane,

[0115] Silane coupling agents having epoxy groups, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 3-glycidyloxypropyltriethoxysilane, and 8-glycidyloxyoctyltrimethoxysilane,

[0116] Silane coupling agents having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane,

[0117] Silane coupling agents having an amino group such as N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-ethoxysilyl-N-(1,3-dimethylbutylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and the hydrochloride of N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane,

[0118] Silane coupling agents having urea groups, such as 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane,

[0119] Silane coupling agents having halogen atoms such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane,

[0120] Silane coupling agents having a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane,

[0121] Silane coupling agents having a sulfide group such as bis(trimethoxysilylpropyl)tetrasulfide and bis(triethoxysilylpropyl)tetrasulfide;

[0122] Silane coupling agents having an isocyanate group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane,

[0123] Silane coupling agents having allyl groups, such as allyltrichlorosilane, allyltriethoxysilane, and allyltrimethoxysilane,

[0124] Silane coupling agents having a hydroxyl group, such as 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane, etc.

[0125] These silane coupling agents can be used alone or in combination of two or more.

[0126] When the sealant layer contains a silane coupling agent, the content of the silane coupling agent in the entire sealant layer is preferably 0.01 to 5% by mass, more preferably 0.05 to 1% by mass.

[0127] [Other ingredients]

[0128] The sealant layer may contain other components within a range that does not inhibit the effects of the present invention.

[0129] Examples of other components include additives such as ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, fillers, pigments, extenders, and softeners.

[0130] These can be used individually by 1 type or in combination of 2 or more types.

[0131] When the sealant layer contains these additives, the content thereof can be appropriately determined according to the purpose.

[0132] [Sealing agent layer]

[0133] The thickness of the sealant layer is usually 1 to 50 μm, preferably 1 to 25 μm, and more preferably 5 to 25 μm. The sealant layer having a thickness within the above range is suitable for use as a material for forming a sealant.

[0134] The thickness of the sealant layer can be measured using a known thickness meter in accordance with JIS K 7130 (1999).

[0135] The method for forming the sealant layer is not particularly limited. For example, the sealant layer can be formed using a casting method.

[0136] When the sealant layer is produced by a casting method, a sealant composition containing components constituting the sealant layer is prepared, and the obtained sealant composition is applied to a substrate or a release layer of a release film that has been subjected to a release treatment by a known method, and the obtained coating is dried to form the sealant layer.

[0137] The sealant composition may contain a solvent.

[0138] Examples of the solvent include aromatic hydrocarbon solvents such as benzene and toluene, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane, and alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane and methylcyclohexane.

[0139] These solvents can be used alone or in combination of two or more.

[0140] The content of the solvent can be appropriately determined in consideration of coating properties and the like.

[0141] Examples of a method for applying the sealant composition include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0142] Examples of a method for drying the coating film include conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation.

[0143] The conditions for drying the coating film are, for example, 80 to 150° C. for 30 seconds to 5 minutes.

[0144] When the sealant layer has thermosetting properties, by heating the sealant layer, at least the cyclic ether group of the cyclic ether group-containing compound (B) reacts, and the sealant layer is cured.

[0145] The conditions for thermally curing the sealant layer are not particularly limited.

[0146] The heating temperature is usually 80 to 200°C, preferably 90 to 150°C.

[0147] The heating time is usually 30 minutes to 12 hours, preferably 1 to 6 hours.

[0148] The dielectric loss tangent of the cured product of the sealant layer at 23° C. and a frequency of 100 kHz (hereinafter, this dielectric loss tangent may be referred to as “dielectric loss tangent (β)”) is preferably 0.05 or less, more preferably 0.045 or less, and even more preferably 0.040 or less.

[0149] The lower limit of the dielectric loss tangent (β) is not particularly limited, but is usually 0.0001 or more.

[0150] By setting the dielectric loss tangent (β) to be 0.05 or less, heat generation and signal attenuation can be suppressed.

[0151] The dielectric loss tangent (β) can be measured according to the method described in the examples.

[0152] Since the sealant layer of the sealing sheet of the present invention contains the cyclic ether group-containing compound (B), the dielectric loss tangent of the cured product thereof tends to be low.

[0153] The total light transmittance of the cured product of the sealant layer is preferably 90% or more, more preferably 91% or more.

[0154] The upper limit of the total light transmittance is not particularly limited, but is usually 100% or less.

[0155] By using a cured product having a total light transmittance of 90% or more as a sealing material in a display device such as a touch panel, an electronic device with better visibility can be obtained.

[0156] The total light transmittance can be measured according to the method described in the Examples.

[0157] Since the sealant layer of the sealing sheet of the present invention contains the cyclic ether group-containing compound (B), the total light transmittance of the cured product thereof tends to be high.

[0158] The haze value of the cured product of the sealant layer is preferably 1% or less, more preferably 0.9% or less, and particularly preferably 0.4% or less.

[0159] The lower limit of the haze value is not particularly limited, but is usually 0% or more.

[0160] By using a cured product having a haze value of 1% or less as a sealing material in a display device such as a touch panel, an electronic device with better visibility can be obtained.

[0161] The haze value can be measured according to the method described in the examples.

[0162] Since the sealant layer of the sealing sheet of the present invention contains the cyclic ether group-containing compound (B), the haze value of the cured product thereof tends to be reduced.

[0163] The b* value of the cured product of the sealant layer in the CIE 1976 L*a*b* color space is preferably not less than -1 and not more than +1.

[0164] By using a cured product having a b* value within the above range as a sealing material in a display device such as a touch panel, an electronic device with better visibility can be obtained.

[0165] The b* value can be measured according to the method described in the Examples.

[0166] Since the sealant layer of the sealing sheet of the present invention contains the cyclic ether group-containing compound (B), the b* value tends to be close to zero.

[0167] [Sealing sheet]

[0168] The sealing sheet of the present invention has the above-mentioned sealant layer.

[0169] The sealing sheet of the present invention may have a substrate, a release film, a functional film, and the like in addition to the sealant layer.

[0170] As the substrate, a resin film is generally used.

[0171] The resin component of the resin film includes polyimide, polyamide, polyamideimide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyarylate, acrylic resin, cycloolefin polymer, aromatic polymer, polyurethane polymer, liquid crystal polymer film, etc.

[0172] The thickness of the substrate is not particularly limited, but is preferably 10 to 500 μm, more preferably 10 to 300 μm, and further preferably 15 to 200 μm.

[0173] The release film functions as a support in the production process of the sealing sheet, and functions as a protective sheet for the sealant layer until the sealing sheet is used.

[0174] In addition, when using the sealing sheet of this invention, a release film is usually peeled and removed.

[0175] As the release film, a conventionally known release film can be used. For example, a release film having a release layer subjected to a release treatment with a release agent on a release film substrate can be cited.

[0176] Examples of the release film substrate include paper substrates such as glassine paper, coated paper, and high-quality paper, laminated paper obtained by laminating thermoplastic resins such as polyethylene on these paper substrates, and plastic films such as polyethylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate resins, polypropylene resins, and polyethylene resins.

[0177] Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorine resins.

[0178] The thickness of the release film is not particularly limited, but is usually about 20 to 250 μm.

[0179] When the sealing sheet of the present invention has a release film, the sealing sheet may have one release film on each side of the sealing compound layer, or two release films in total, or may have a release film only on one side of the sealing compound layer.

[0180] Examples of the functional film include conductive films, gas barrier films, antireflection films, phase difference films, viewing angle enhancement films, brightness enhancement films, etc. Among them, for example, examples of the gas barrier film include films having a metal or inorganic compound film.

[0181] The thickness of the functional film is not particularly limited, but is usually 5 to 200 μm, preferably 10 to 100 μm.

[0182] The sealant layer of the sealing sheet of the present invention is suitably used as a material for forming a sealing material for electronic devices.

[0183] The sealant layer of the sealing sheet of the present invention provides a cured product having low dielectric properties. Since this property can be utilized, the electronic device is preferably an electronic device including a touch sensor such as a touch panel.

[0184] In addition, the sealant layer of the sealing sheet of the present invention provides a cured product having excellent transparency. Since this property can be utilized, the electronic device is preferably an electronic device requiring light transparency.

[0185] Electronic devices requiring light transmittance include organic EL elements such as organic EL displays and organic EL lighting, liquid crystal elements such as liquid crystal displays, electronic paper elements, solar cell elements, light emitting diodes, and the like.

[0186] The method of sealing an electronic device using the sealing sheet of the present invention is not particularly limited. For example, the electronic device can be sealed by attaching the sealant layer of the sealing sheet of the present invention to the target electronic device and then curing the sealant layer by the above-mentioned method.

[0187] Example

[0188] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0189] [Compounds used in Examples or Comparative Examples]

[0190] Phenoxy resin (A1): (Mitsubishi Chemical Corporation, trade name: YX6954BH30, glass transition temperature (Tg): 130°C, epoxy equivalent: 10,000 to 16,000 g / eq)

[0191] Phenoxy resin (A2): (Mitsubishi Chemical Corporation, trade name: 1256B40, glass transition temperature (Tg): 98°C, epoxy equivalent: 6,700 to 8,000 g / eq)

[0192] Phenoxy resin (A3): (manufactured by Mitsubishi Chemical Corporation, trade name: YX8100BH30, glass transition temperature (Tg): 150°C)

[0193] Compound having a cyclic ether group (B1): hydrogenated bisphenol A type epoxy resin [Mitsubishi Chemical Corporation, trade name: YX8034, cyclic ether equivalent: 270 g / eq, a compound having an alicyclic skeleton and a glycidyl ether group, and being liquid at 25°C]

[0194] Compound having a cyclic ether group (B2): hydrogenated bisphenol A type epoxy resin [Mitsubishi Chemical Corporation, trade name: YX8000, cyclic ether equivalent: 205 g / eq, a compound having an alicyclic skeleton and a glycidyl ether group, and being liquid at 25°C]

[0195] Compound having a cyclic ether group (BX1): bisphenol A type epoxy resin [Mitsubishi Chemical Corporation, trade name: jER828, cyclic ether equivalent: 189 g / eq, a compound having an aromatic skeleton and a glycidyl ether group, and being liquid at 25°C]

[0196] Thermal cationic polymerization initiator (C1): (manufactured by Sanshin Chemical Co., Ltd., trade name: SAN-AID SI-B3)

[0197] Silane coupling agent (D1): 8-glycidyloxyoctyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM4803)

[0198] [Example 1]

[0199] 100 parts by mass of a phenoxy resin (A1), 150 parts by mass of a compound having a cyclic ether group (B1), 3.3 parts by mass of a thermal cationic polymerization initiator (C1), and 0.2 parts by mass of a silane coupling agent (D1) were dissolved in methyl ethyl ketone to prepare a coating liquid.

[0200] The coating liquid was applied to the release-treated surface of a release film (first release film, manufactured by LINTEC Corporation, trade name: SP-PET752150), and the resulting coating was dried at 100° C. for 2 minutes to form a sealant layer having a thickness of 15 μm. The release-treated surface of another release film (second release film, manufactured by LINTEC Corporation, trade name: SP-PET381130) was bonded to the sealant layer to obtain a sealing sheet.

[0201] [Examples 2 to 3, Comparative Examples 1 and 2]

[0202] Except having changed the kind and amount of each component which comprises a sealant layer into the conditions described in Table 1, it carried out similarly to Example 1, and obtained the sealing sheet.

[0203] The following tests were performed on the sealing sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2. Table 1 shows the results.

[0204] [Relative dielectric constant, dielectric loss tangent]

[0205] The sealing sheet obtained in the example or the comparative example was heated at 110° C. for 1 hour to cure the sealing agent layer. The release film was peeled off from the sealing sheet after the curing treatment to obtain a sample for measurement.

[0206] The relative dielectric constant and dielectric loss tangent of the obtained measurement sample were measured at 23° C. and 100 kHz by a self-balancing bridge method using an LF impedance analyzer (HP4192A manufactured by Agilent Technology Co., Ltd.).

[0207] [Total light transmittance]

[0208] The release film of one sealing sheet obtained in the example or comparative example was peeled off to expose the sealant layer. The exposed sealant layer was bonded to an alkali-free glass at 23°C using a laminator to obtain a laminate. The obtained laminate was heated at 110°C for 1 hour to cure the sealant layer, and then the other release film was peeled off to obtain a sample for measurement.

[0209] The total light transmittance (%) of the obtained measurement sample was measured using a haze meter (NDH-2000, manufactured by Nippon Denshoku Industries, Ltd.) in accordance with JIS K7361:1997.

[0210] [Haze]

[0211] The same measurement sample as that used for the total light transmittance was prepared.

[0212] The haze value (%) of the obtained measurement sample was measured using a haze meter (NDH-2000 manufactured by Nippon Denshoku Industries, Ltd.) in accordance with JIS K7136:2000.

[0213] [Color measurement]

[0214] The same measurement sample as that used for the total light transmittance was prepared.

[0215] The obtained measurement sample was measured for color value b* defined in CIE 1976 L*a*b* colorimetric system using a spectrophotometer (UV-3200 manufactured by Shimadzu Corporation) in accordance with JIS Z 8729-1994.

[0216] [Table 1]

[0217] Table 1

[0218]

[0219] The following can be seen from Table 1.

[0220] Since the sealant layer of the sealing sheets obtained in Examples 1 to 3 contains a large amount of the compound having an alicyclic skeleton and a cyclic ether group [cyclic ether group-containing compound (B)], the cured product thereof has low dielectric properties and excellent transparency.

[0221] On the other hand, the dielectric constant of the cured product of the sealant layer of the sealing sheet obtained in Comparative Examples 1 and 2 using a compound having an aromatic skeleton and a cyclic ether group instead of the cyclic ether group-containing compound (B) was increased.

Claims

1. A sealing sheet having a curable sealant layer, characterized in that: Satisfy the following requirements (I), (II) and (III): Requirement (I): The sealant layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher; Requirement (II): The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group; Requirement (III): The relative dielectric constant of the cured product of the sealant layer at 23° C. and a frequency of 100 kHz is 3.5 or less, The content of the compound having an alicyclic skeleton and a cyclic ether group is 55 to 70% by mass based on the entire sealant layer.

2. The sealing sheet according to claim 1, wherein The cured product of the sealant layer has a dielectric loss tangent of 0.05 or less at 23° C. and a frequency of 100 kHz.

3. The sealing sheet according to claim 1 or 2, wherein: At least one of the compounds having an alicyclic skeleton and a cyclic ether group is a liquid compound at 25°C.

4. The sealing sheet according to claim 1 or 2, wherein: At least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound having a glycidyl ether group as the cyclic ether group.

5. The sealing sheet according to claim 1 or 2, wherein: The cured product of the sealant layer has a total light transmittance of 90% or more.

6. The sealing sheet according to claim 1 or 2, wherein: The cured product of the sealant layer has a haze value of 1% or less.

7. The sealing sheet according to claim 1 or 2, wherein: The cured product of the sealant layer has a b* value of -1 or more and +1 or less in the CIE 1976 L*a*b* color space.

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